Safety Planning Study of Urban Freeways

Safety-conscious planning is a relatively new concept. It was developed in response to safety-related provisions of the Transportation Equity Act for the 21st Century (TEA-21) of 1998, which required explicit consideration of safety in the transportation planning process. The problem of using accident rates in transportation planning is revisited, and a case history of applying safety-conscious planning methods by the Colorado Department of Transportation is reviewed. A two-phase process that has been used to evaluate the safety impacts of multiple design alternatives is introduced. The evaluation process is based on the available safety performance functions calibrated specifically for urban freeways in concert with diagnostic investigations, pattern recognition analysis, and detailed accident diagramming. The critical importance of accident diagramming is discussed in reference to examining safety history at complex interchange locations.